Laser ablation catheters having expanded distal tip windows for efficient tissue ablation

ABSTRACT

Laser ablation catheters and methods of using same for efficient tissue ablation are disclosed. In some cases, laser ablation catheter embodiments may include expanded distal tips that allow for beam energy expansion and reduce dead space at the distal cutting surface of the laser ablation catheter.

RELATED APPLICATIONS

This application is a continuation of copending U.S. patent applicationSer. No. 16/734,202, filed Jan. 3, 2020, entitled LASER ABLATIONCATHETERS HAVING EXPANDED DISTAL TIP WINDOWS FOR EFFICIENT TISSUEABLATION, by J. Laudenslager et al., which is a continuation of U.S.patent application Ser. No. 15/359,412, filed Nov. 22, 2016, now U.S.Pat. No. 10,555,772, issued Feb. 11, 2020, entitled LASER ABLATIONCATHETERS HAVING EXPANDED DISTAL TIP WINDOWS FOR EFFICIENT TISSUEABLATION, by J. Laudenslager et al., which claims priority under 35U.S.C. Section 119(e) from U.S. Provisional Patent Application Ser. No.62/258,836, filed Nov. 23, 2015, by J. Laudenslager et al., titledENLARGED SHAPED DISTAL WINDOW TIPS FOR LASER ABLATION CATHETERS, each ofwhich is incorporated by reference herein in its entirety.

BACKGROUND

Some pulsed laser energy transmitting catheters currently used forablating and clearing blockages in human arteries may use a single largediameter fiber optic which tends to be stiff for some such indications.For improved catheter flexibility, multiple smaller diameter fiberoptics may be used which are arranged in various shaped bundles. In somecases, excimer laser ablation efficiency of atheroma may be inverselyproportional to the relative amount of inactive surface area or deadspace at the ablation catheter tip contacting the target surface beingablated. Multiple fiber optic based catheters may have a significantamount of dead space, which may be due to the cladding, buffer, fiberpacking factor, glue and the sidewall of the catheter outside tubingalong with a guidewire lumen tubing or the like.

A doctoral thesis by Hamburger showed ablation histology for multiplefiber optic bundle ablation catheters versus a single fiber optic andindicated that the dead space leads to more tissue damage and lessefficient ablation than a window tip with a homogonous energydistribution ablating surface, “New Aspects of Excimer Laser CoronaryAngioplasty Physical Aspects and Clinical Results, printed by OptimaGrafische Communicatie ISBN 90-73235-27-8, Rotterdam, Jaap N. Hamburger,1999. Hamburger's conclusions stated that: “Optimization of excimerlaser coronary angioplasty can be achieved by elimination ofultraviolet-absorbing media, reduction of catheter advancement speedsand by reduction of the non-light emitting area at the tip of a lasercatheter.” What are needed are catheter device configurations andmethods for use thereof which allow for increased optical beam expansionof the optical beam which exits the distal portion of the catheter andwhich reduce dead space due to catheter elements which encompass anoptical window at a distal portion of a laser catheter.

SUMMARY

Some embodiments of a laser ablation catheter to ablate blockages inbody lumens using high energy and high power laser pulses include aliquid filled waveguide. The liquid filled waveguide may include anelongate catheter body tube having an inner surface with a first indexof refraction and a biocompatible ultraviolet transparent optical fluiddisposed within and completely filling a core liquid volume of theelongate catheter body tube which is at least partially bounded by theinner surface, with the optical fluid having a second index ofrefraction which is greater than the first index of refraction. Thelaser ablation catheter may also include an ultraviolet grade elongateddistal optical window disposed in liquid sealed relation to a surface ofthe elongate catheter body tube at a distal end of the elongate catheterbody tube. The distal optical window may further have an insert segmentwhich is disposed within a distal section of the elongate catheter bodytube and which includes a core and cladding configured to act as awaveguide. The distal optical window may also have an expanded segmentwhich is disposed distally of the insert segment, which does not have acore and cladding configured to act as a waveguide, which has an outerdiameter which is greater than an outer diameter of the insert segment,which has an output surface that has an area which is equal to orgreater than an area of a transverse section of the elongate catheterbody tube proximally adjacent the distal optical window and which has anaxial length sufficient to allow optical energy expansion within theexpanded segment such that a optical energy emitted from the outputsurface produces a hole in target tissue having a diameter equal to orgreater than an outer diameter of the elongate catheter body tubeproximally adjacent the distal optical window.

Some embodiments of a laser ablation catheter to ablate blockages inbody lumens using high energy laser pulses with a pulse duration of lessthan 100 nanoseconds may include a liquid filled waveguide including anelongate catheter body tube having an inner surface with a first indexof refraction and a biocompatible ultraviolet transparent optical fluiddisposed within and completely filling an inner lumen of the elongatecatheter body tube, with the optical fluid having a second index ofrefraction which is greater than the first index of refraction. Suchlaser ablation catheters may also include an ultraviolet grade elongateddistal optical window disposed in liquid sealed relation to a surface ofthe elongate catheter body tube at a distal end of the elongate catheterbody tube. The distal optical window may further have an insert segmentwhich is disposed within a distal section of the elongate catheter bodytube and which comprises an ultraviolet grade material. A layer ofmaterial may be disposed about an outer surface of the insert segmentwhich includes an index of refraction lower than an index of refractionof the material of the insert segment or a reflective material. Inaddition, the distal optical window may further include an expandedsegment which is disposed distally of the insert segment, which is notconfigured to act as a waveguide, which has an outer diameter which isgreater than an outer diameter of the insert segment, which has anoutput surface that has an area which is equal to or greater than anarea of a transverse section of the elongate catheter body tubeproximally adjacent the distal optical window and which has an axiallength sufficient to allow optical energy expansion within the expandedsegment such that optical energy emitted from the output surface ablatesa hole in target tissue having a diameter equal to or greater than anouter diameter of the elongate catheter body tube proximally adjacentthe distal optical window.

Some embodiments of a laser ablation catheter to ablate blockages inbody lumens may include a liquid filled waveguide including an elongatecatheter body tube having an inner layer with a first index ofrefraction and a biocompatible ultraviolet transparent optical fluiddisposed within and completely filling a core liquid volume of theelongate catheter body tube, with the optical fluid having a secondindex of refraction which is greater than the first index of refraction.The laser ablation catheter may also include a distal optical windowdisposed in liquid sealed relation to the elongate catheter body tube ata distal end of the elongate catheter body tube. The distal opticalwindow may further have an insert segment which is disposed within adistal section of the catheter body tube and which includes a core andcladding configured to act as a waveguide. An expanded segment may bedisposed distally of the insert segment which is not configured to actas a waveguide, which has an outer diameter which is greater than anouter diameter of the insert segment, which has an output surface thathas an area which is equal to or greater than an area of a transversesection of the elongate catheter body tube proximally adjacent thedistal optical window and which has an axial length sufficient to allowoptical energy expansion within the expanded segment such that opticalenergy emitted from the output surface produces a hole in target tissuehaving a diameter equal to or greater than an outer diameter of theelongate catheter body tube proximally adjacent the distal opticalwindow.

Certain embodiments are described further in the following description,examples, claims and drawings. These features of embodiments will becomemore apparent from the following detailed description when taken inconjunction with the accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a laser system embodiment including alaser and a disposable liquid core laser ablation catheter coupled tothe laser.

FIG. 2 is an elevation view of a distal section of a liquid core laserablation catheter embodiment including a tapered window housing whichincorporates an optical window having an expanded segment with asubstantially flat output surface.

FIG. 2A is an elevation view of a proximal end of the liquid core laserablation catheter of FIG. 2.

FIG. 3 is a transverse section view of the liquid core laser ablationcatheter of FIG. 2.

FIG. 4 is a longitudinal section view of the distal section of theliquid core laser ablation catheter embodiment of FIG. 2 which includesa distal optical window embodiment having an insert segment and anexpanded segment, a tapered window housing, a catheter body tube, and anoptical fluid disposed within the catheter body tube.

FIG. 5 is a longitudinal section view of a distal section of a liquidcore laser ablation catheter embodiment which includes an optical windowhaving a constant diameter, a tapered window housing, a catheter bodytube, and an optical fluid disposed within the catheter body tube.

FIG. 6 is a transverse section view of the liquid core laser ablationcatheter of FIG. 5.

FIG. 7 is a longitudinal section view of a liquid core laser ablationcatheter embodiment distal section which includes an optical windowhaving an insert segment and an expanded segment with a rounded and/orchamfered distal edge, a non-tapered window housing, a catheter bodytube, and an optical fluid disposed within the catheter body tube.

FIG. 8 is a transverse section view of the liquid core laser ablationcatheter embodiment of FIG. 7.

FIG. 9 is a longitudinal section view of a liquid core laser ablationcatheter embodiment distal section which includes an optical windowhaving an insert segment and an expanded segment with a substantiallyflat output surface and a rounded distal edge, a tapered metal housing,a catheter body tube, an optical fluid disposed within the catheter bodytube, and an eccentric guide wire lumen which is disposed on an exteriorsurface of the catheter body tube.

FIG. 10 is a transverse section view of the liquid core laser ablationcatheter embodiment of FIG. 9.

FIG. 11 is an elevation view of a fiber optical window embodiment havinga constant diameter with a flat polished distal surface withsubstantially non-rounded edges.

FIG. 12 is an elevation view of an optical window embodiment having aninsert segment, an expanded segment, and a substantially flat outputsurface.

FIG. 12A is a transverse section view of the proximal insert segment ofthe optical window embodiment of FIG. 12 which shows a fiber core andcladding configuration.

FIG. 12B is a transverse section view of the expanded segment of theoptical window embodiment of FIG. 12 without any cladding layer.

FIG. 13 is an elevation view of an optical window embodiment having aninsert segment, an expanded segment, and a substantially convex outputsurface with rounded edges.

FIG. 14 is an elevation view of an optical window embodiment having aninsert segment, an expanded segment, and a substantially concave outputsurface with rounded edges.

FIG. 15 is an elevation view of a tapered metal window housingembodiment.

FIG. 16 is an elevation view of the tapered window housing embodiment ofFIG. 15 and an optical window embodiment having a constant diameterdisposed within and secured to the tapered window housing.

FIG. 17 is an elevation view of the tapered window housing embodiment ofFIG. 15 and an optical window embodiment having an insert segment and anexpanded segment disposed within and secured to the tapered windowhousing.

FIG. 18 is an elevation view in longitudinal section that shows theliquid core laser ablation catheter embodiment of FIG. 5 cutting througha lesion is a body lumen.

FIG. 19 is an elevation view in longitudinal section of the liquid corelaser ablation catheter embodiment of FIG. 4 cutting through a lesion ina body lumen.

FIG. 20 is an elevation view of the liquid core laser ablation catheterof FIG. 19 being advanced into target tissue of the lesion duringablation.

The drawings illustrate embodiments of the technology and are notlimiting. For clarity and ease of illustration, the drawings may not bemade to scale and, in some instances, various aspects may be shownexaggerated or enlarged to facilitate an understanding of particularembodiments.

DETAILED DESCRIPTION

Laser ablation catheters and laser delivery systems in general have awide range of applications in the medical field. Such systems may beused to deliver laser energy to desired sites of a patient's anatomy,and may be particularly suitable for delivering laser energy tolocations inside a patient's body that allow for minimally invasivetreatment of a variety of indications using a variety of treatmentmodalities. Example of some treatment modalities include, heatingtissue, stimulating tissue, drug activation within a patient's tissueand ablation of tissue or other organic or calcium materials within apatient. Some examples of clinical indications for laser treatment mayinclude laser atherectomy and the use of a laser catheter to cross totalor partial occlusions of body vessels.

One drawback of some current laser systems is the cost of the systemsand devices used to deliver the laser energy, particularly thosecomponents that are designated as single use products. Liquid core laserablation catheter embodiments may generally be considerably lessexpensive than a silica fiber optic based laser catheter and may alsohave less dead space at the ablation tip for contact cutting. Liquidfilled ablation catheters may eliminate most of the dead space inside acatheter body tube compared to multiple fiber optic bundles but maystill have residual dead space, which consists of the distal fiberwindow cladding and the outside wall of the metal tip or catheter tubethat holds the window. Using a tapered metal tip, as disclosed for aliquid filled catheter in co-owned patent application number U.S. patentapplication Ser. No. 13/651,070, Publication No. 2013/0096545, filed byJ. Laudenslager et al., on Oct. 12, 2012, titled Small Flexible LiquidCore Catheter for Laser Ablation in Body Lumens and Methods for Use,which is hereby incorporated by reference herein in its entirety,minimizes the initial dead space. For example, a 5 French liquid filledablation catheter with a tapered metal tip may have a 70 percent activearea at the tip that gradually reduces to 42 percent once the cathetertip penetrates the target past the tapered metal sheath. Multiple fiberoptic based catheters, ignoring the guide wire lumen, may have about 17percent to 30 percent active cutting area in some cases depending on thedesign at the tip. Multiple fiber optic based catheters may need to beoperated at higher energy fluences and repetition rates compared tofluences and repetition rates of single fiber optic systems or the likein order to cut as efficiently as a laser ablation catheter having ahomogenous laser energy output at the output surface of the distaloptical window.

Liquid core laser ablation catheters discussed herein have less deadspace and needs less energy density to ablate tissue compared generallyto multiple fiber optic laser ablation catheter designs currently incommercial use. The reduced dead space (that distal surface area that isnot emitting laser energy) may be an important feature for ablation ofblockages in arteries and for the ability of the laser ablation catheterto cross a lesion in a patient's vessel. Some embodiments of liquid corelaser ablation catheters may incorporate an optical window having anexpanded segment with a stepped configuration which is configured toincrease the output surface of the liquid core laser ablation catheter,minimize the dead space of the liquid core laser ablation catheter, andallow for easier passage of the liquid core laser ablation catheterthrough tight lesions which are disposed within the vasculature of apatient with less pulse energy needed.

Some embodiments of a laser ablation system may include a laser energysource and a liquid core laser ablation catheter. Some embodiments ofthe system may also include a laser coupler which is disposed at aproximal section of the liquid core laser ablation catheter. The liquidcore laser ablation catheter may include a working length section whichis disposed between the proximal section and a distal section of theliquid core laser ablation catheter. The working length section of theliquid core laser ablation catheter may include a catheter body tubewhich may feature an inner lumen which is disposed within the catheterbody tube.

In some cases, the inner lumen may be coated with an optical coating,with the optical coating spanning the working length section. An opticalfluid may be disposed within a core liquid volume at least partiallybounded by the inner lumen of the catheter body tube, with the opticalfluid being in optical communication with the laser coupler. The distalsection of the liquid core laser ablation catheter may include a windowhousing having a tubing cavity which may be secured to the catheter bodytube. An optical window may be partially disposed within and secured tothe window housing, in optical communication with the optical fluid.

Some embodiments of the distal optical window may include an expandedsegment which has an outer radial surface that extends radially beyondan outer radial surface of an insert segment of the optical window, withan outer surface of the insert segment being configured to couple to aninterior window surface of the window housing. The expanded segment mayextend distally beyond a distal portion and/or distal end of the windowhousing. In some cases, the outer diameter of the expanded segment maybe equal to or greater than an outer diameter of the window housing,thereby allowing optical energy which exits the optical window throughan output surface of the expanded segment to ablate a surface area oftarget material which is greater than or equal to the surface area ofthe distal section of the liquid core laser ablation catheter. In somecases the optical window which includes the insert segment and theexpanded segment may be formed from a single length of ultraviolet gradesilica over silica core-clad fiber optic.

Some liquid core laser ablation catheter embodiments may be configuredsuch that optical energy may be transmitted from the laser energy sourcethrough the laser coupler, through the optical fluid which disposedwithin the core liquid volume in the inner lumen of the catheter bodytube, through the optical window where it exits the output surface ofthe expanded segment, and into target tissue and/or target materialwhich is to be ablated by the optical energy. In some cases the laserenergy source may be configured as an ultraviolet laser and the opticalenergy may be configured as pulsed ultraviolet energy, with eachultraviolet energy pulse having sufficient pulse energy to ablateblockages in body lumens at the distal tip of the liquid core laserablation catheter when it is curved around typical bends in a patient'svascular system. Some laser energy sources may be configured as an XeClexcimer laser with a wavelength around 308 nm, with a pulse durationgreater than about 10 nanoseconds (nsec), a pulse energy fluence greaterthan about 6 milli-Joules per millimeter squared (mJ/mm²) delivered tothe distal tip of the liquid core laser ablation catheter and arepetition rate range of about 10 Hertz (Hz) to about 100 Hz. In somecases, such laser energy sources may be operated with pulse durationsless than about 300 nsec, more specifically, less than about 100 nsec.

Some distal optical window embodiments may be formed monolithically froma single uninterrupted piece of feed fiber optic which is made ofultraviolet grade silica over silica which form a core and cladding ofthe feed fiber optic. The expanded segment of the optical window may beformed by melting a portion of the core-cladding materials of the feedfiber optic into a melted portion and forming the expanded segment fromthe melted portion. The portion of the feed fiber optic which has notbeen melted may include the insert portion of the optical window. Insome cases, within the expanded segment of the optical window thecladding material may be mixed with the core material resulting in anexpanded segment of the distal optical window that has no cladding orwaveguide configuration, nor does it have any dead space. An outerdiameter of the expanded segment may be larger than an outer radialdiameter of the insert segment, and the diameter of the expanded segmentmay be greater than or equal to diameters of the tip or distal edge ofthe window housing and/or the catheter body tube proximally adjacent thedistal optical window which may have a stepped configuration in somecases.

For some embodiments of distal optical windows (which may typicallyserve as output optical windows), the axial length of the expandedsegment may be configured to be long enough to allow for an optical beamto expand to an outer diameter of the output surface of the expandedsegment. The length of the expanded segment may also be configured to beaxially short enough to allow for passage through tortuous pathwayswithin a human patient's anatomical lumen. For some embodiments of sucha distal optical window, the overall length of the optical window may befrom about 4 millimeters (mm) to about 8 mm. For some embodiments of theoptical window, the axial length of the expanded segment may be fromabout 0.5 mm to about 2 mm, more specifically, about 1 mm to about 2 mmin some cases. For some embodiments, the axial length of the expandedsegment 48 may be 0.9 mm to 1.1 mm. The ratio of the diameter of theexpanded segment to the diameter of the insert segment may be about fromabout 1.1:1 to about 1.5:1 in some cases.

Some or all of the edges of any distal optical window embodimentsdiscussed herein may be filleted, rounded or chamfered in order tominimize damage or chipping during assembly, and to prevent trauma toadjacent tissue when disposed within a body lumen. For some opticalwindow embodiments, the expanded segment and the insert segment of theoptical window may be monolithically formed from sapphire windowmaterial or substrate including a feed fiber optic substrate. Someembodiments of optical windows having an expanded segment and an insertsegment may be formed monolithically from a single piece of material,while other embodiments of optical windows having an expanded segmentand an insert segment may be formed by welding or fusing differentpieces of material together.

FIG. 1 shows a laser ablation system embodiment 10 that includes a laserenergy source 12 having a housing 14, a power cord 16, an activationfootswitch 18, a control panel 20 and an output coupler 22. A liquidcore laser ablation catheter 24 may include a laser coupler 26 which isdisposed at a proximal section 28 of the ablation catheter 24 and whichmay be coupled to the output coupler 22 of the laser source 12 as shown.The ablation catheter 24 may be disposed within an inner lumen of asupport catheter 30 which maybe used to guide or support the liquid corelaser ablation catheter 24 within a body lumen of a patient. The supportcatheter 30 may include a Y-adapter 32 which is coupled to the proximalend 34 of the support catheter 30. The liquid core laser ablationcatheter 24 may be disposed within and pass through a central lumen (notshown) of the Y-adapter 32, and a syringe 33 which may contain a normalsaline solution that may be used to flush blood and contrast fluid froma distal window 80 of the ablation catheter 24 during ablationprocedures. The support catheter 30 may also incorporate a radiopaquemarker 36 which is disposed at a distal section 38 of the supportcatheter 30, the radiopaque marker 36 facilitating the visualization ofthe support catheter 30 when viewed under fluoroscopy.

A working length 42 of the liquid core laser ablation catheter 24 mayinclude the length inside the patient's body between the access pointand the target tissue lesion site and the length outside the patient'sbody necessary to couple or pass through the Y-adapter. An additionallength may be needed to couple the working length 42 of 50 centimeters(cm) to 120 cm to the laser source 12 in some cases. If a laser source12 is large and located away from the patient, an additional workinglength 42 may be necessary. Some liquid core laser ablation catheterembodiments 24 may be from about 2 meters to about 3 meters long in somecases.

In some cases, the laser source 12 of the laser system 10 may include aXeCl excimer laser which produces high energy pulses at a wavelength ofabout 308 nm, for example, 307 nm to 309 nm, however, other high energypulsed ultraviolet laser sources may be used. Some laser sourceembodiments 12 may have a pulse duration of less than about 100 nsec anda repetition rate of up to about 100 Hz. Some such laser sourceembodiments 12 may be capable of producing about 20 milli-Joules perpulse (mJ/pulse) to about 100 mJ/pulse. For some embodiments, thetransmission of laser optical energy through the liquid core laserablation catheter with solid windows may be high enough to enable arelatively small laser source 12 to be used for the laser ablationsystem 10 in order to save cost and valuable catheter lab space. Incontrast some previous embodiments of ablation catheters having multiplefibers may have considerable dead space at the input laser coupler,which requires a certain energy density over a larger area and hencerequires higher laser optical energy output and a larger more expensivelaser source 12 to achieve ablation of the target atheroma. In addition,the large dead space at the distal end of such ablation catheters havingmultiple fibers may require a higher energy fluence in order to overcomethe dead space for efficient ablation of atheroma.

FIG. 2 is an enlarged view of the distal section 42 of the liquid corelaser ablation catheter 24 which is depicted in FIG. 1, and of thedistal section 38 and radiopaque marker 36 of the support catheter 30.The distal section 60 of the liquid core laser ablation catheter 24 mayinclude a distal optical window 44 (see FIG. 12) having an insertsegment 46 and an expanded segment 48. The distal optical window 44 maybe partially disposed within a window housing 50 (see FIG. 15), thewindow housing 50 may in turn be secured to a catheter body tube 52. Thecatheter body tube 52 may be fabricated from any suitable polymermaterial. In some cases, the catheter body tube may be extruded from afluorinated ethylene propylene (FEP) fluoropolymer material. For someembodiments, the wall of the catheter body tube may incorporate abraided material or layer 57 (see FIG. 10) which may be disposed withinor otherwise encapsulated by the wall material of the catheter body tube52. The braided material may facilitate the torqueablilty and thepushability of the working length 42 of the liquid core laser ablationcatheter 24.

Some embodiments of the window housing 50 may include a tapered section51 as shown in FIG. 2 wherein an outer profile of the window housing 50is suitably tapered towards the distal end of the window housing 50. Thewindow housing 50 may be formed from any suitable high strength polymeror metal material. For some embodiments, the window housing 50 may befabricated from stainless steel, titanium or other suitable metal thatmay optionally serve as a radiopaque marker that may be visualized byimaging systems such as a fluoroscopy system. An interior lumen 53 ofthe catheter body tube as shown in FIG. 4 may contain an optical fluid55, with the optical fluid having an index of refraction (IR) which maydepend on the wavelength of the optical energy which is transmittedthrough the optical fluid 55. For some embodiments the IR of the opticalfluid 55 may be about 1.35 to about 1.38 for optical energy which istransmitted at a wavelength of about 308 nm, with the optical fluid 55being configured to transmit optical energy between the wavelengths ofabout 306 nm to about 310 nm. For some embodiments, the optical fluidmay be water or saline. The distal section 42 of the liquid core laserablation catheter 24 may be configured to be flexible enough to maneuveraround the bends in a patient's vessel without kinking, yet be stiffenough to be able to push the liquid core laser ablation catheter 24through a patient's body vessel while ablating blockages. The opticalfluid 55 may be sealed within the interior lumen 53 of the catheter bodytube 52 by the distal optical window 44 which is disposed in liquidsealed relation to a surface the catheter body tube 52 at a distal endthereof and an input optical window 45 which may be disposed in a liquidsealed relation with a proximal end of the catheter body tube 52 (seeFIG. 2A). For some embodiments, it may be an outer surface of the insertsegment 46 that is in liquid sealed relation to the inner surface 67 ofthe catheter body tube 52.

For some embodiments of the liquid core laser ablation catheter 24, anexterior surface 54 of the insert segment 46 of the optical window 44may be bonded to an interior window surface 56 of the window housing 50using a suitable adhesive 58 as shown in FIG. 17. A distal section 60 ofthe catheter body tube 52 may be notched such that it can be coupled toa tube cavity 62 of the window housing 50 as shown in FIG. 4. A proximalportion 64 of the window housing 50 may be crimped to the distal section60 of the catheter body tube 52 and to a portion of the insert segment46 of the optical window. The crimped section may act to hermeticallyseal the interior lumen 53 which contains the optical fluid 55 from theenvironment which surrounds the liquid core laser ablation catheter 24.The window housing 50, the distal section 62 of the catheter body tube52, the insert segment 46 of the distal optical window 44, and acladding material 66 which encapsulates the insert segment 46 of theoptical window 44 are shown in FIG. 3.

The expanded segment 48 of the distal optical window 44 may extendbeyond a distal edge 68 of the window housing 50 as shown in FIG. 4. Insome cases, it may be desirable for a distal edge of the expandedsegment 48 to have a rounded or chamfered corner 45 as shown in FIG. 2.A diameter 70 of the expanded segment 48 may be greater than or equal toa diameter 72 of the window housing 44 as measured at the distal edge 68of the window housing 44 in some cases. For some distal optical windowembodiments 44 having an insert segment 46 with a core diameter of about1 mm, the expanded segment 48 of the distal optical window 44 may havean outer diameter or transverse dimension 70 of about 1.1 mm to about1.3 mm in some cases, in other cases the outer transverse dimension ofthe expanded segment 48 for such embodiments may be about 1.4 mm toabout 1.6 mm. The distal optical window 44 may have an overall axiallength 72 (including the axial length of the insert segment 46 and theexpanded segment 48, see FIG. 12) selected to minimize stiffness of thedistal section 42 of the liquid core laser ablation catheter 24 butstill allow for sufficient beam expansion within the expanded segment 48so as to fully fill the output surface 80 of the distal optical window44 with optical energy 89. In some cases, the distal optical window 44may have an axial length of less than about 10 mm, more specifically,less than about 8 mm, and even more specifically, less than about 6 mm,to allow the distal section 42 of the liquid core laser ablationcatheter 24 to negotiate curves in when disposed within a patient's bodylumen. For some embodiments of the distal optical window 44, the axiallength of the expanded segment 48 may be about 0.5 mm to about 2 mm, andabout 1 mm to about 2 mm for some embodiments. The ratio of the diameter70 of the expanded segment 48 to the diameter of the insert segment 46for a given distal optical window embodiment 44 may be about from about1.1:1 to about 1.5:1 for some embodiments.

For some embodiments, the insert segment 46 of the distal optical window44 which includes a waveguide fiber optic structure which may have anumerical aperture (NA) in the waveguide structure greater than or equalto a NA of the optical fluid 55 in combination with the inner surface 76of the catheter body tube 52 in order to minimize optical losses at thetransition between optical fluid 55 and the distal optical window 44.That is, the optical fluid 55 disposed within the interior lumen 53 ofthe catheter body tube 52 forms a waveguide structure in combinationwith an inner layer or surface 76 of the catheter body tube 52 based onthe respective IRs of the optical fluid 55 and inner layer 67 so as toinclude a waveguide structure for the catheter body tube 52 having an NAthat is dependent upon those respective IRs. Generally speaking, a firstIR of the inner layer 67 is less than a second IR of the optical fluid55 to produce a waveguide configuration. In some cases, the distaloptical window 44 may include a high NA optical fiber or a silica rodwhich is coated with a relatively low numerical index of refractionmaterial such as an amorphous fluoropolymer coating or a dielectriccoating that is transparent or reflective of the optical energy laserpulse, which may include an ultraviolet energy pulse. FIGS. 13 and 14depict embodiments of the distal optical window 44 with different tipshapes. The distal optical window which is depicted in FIGS. 2, 4, and12 features a substantially flat output surface 80 which is disposed ata distal end 81 of the expanded segment 48. FIG. 13 depicts a distaloptical window embodiment 82 which incorporates a convex output surface84, and FIG. 14 depicts a distal optical window embodiment 86 whichincorporates a concave output surface 88. Any liquid core laser ablationcatheter embodiment discussed herein may incorporate any such distaloptical window shape configuration discussed herein.

In use, the liquid core laser ablation catheter 24 may function toablate target materials or tissue as follows. Referring to FIGS. 1 and12, optical energy 89 transmitted from the laser source 12 enters thelaser coupler 26 of the liquid core laser ablation catheter and is thentransmitted into the optical fluid 55 which is disposed within theinterior lumen 53 of the catheter body tube 52. The optical energy 89 isthen transmitted through the optical fluid 55 along the working length40 of the liquid core laser ablation catheter 24, with an interiorsurface 76 of interior lumen 53 of the catheter body tube 52 acting inconjunction with the optical fluid 55 to form a liquid core waveguide.The optical energy 89 then enters an input surface 78 of the distaloptical window 44, and is transmitted through the insert segment 46 andexpanded segment 48 of the distal optical window 44 as shown in FIG. 2,and then exits the optical window 44 through the output surface 80 ofthe distal optical window 44 and into target material 90 (see FIG. 19).As the optical energy 89 ablates the target material 90, the distaloptical window 44 may be distally advanced into the cavity being formedinto the target material 90 as shown in FIG. 20 in order to maintaincontact or near contact between the output surface 80 and the targetmaterial 90.

An embodiment of a liquid core laser ablation catheter 92 that does notinclude an expanded segment on a distal optical window is shown in FIGS.5, 6, and 18. The liquid core laser ablation catheter 92 may incorporatea constant diameter distal optical window 94 which is depicted in FIG.11. The constant diameter distal optical window 94 may be bonded into atapered window housing 50 with an adhesive 58 as shown in FIG. 16. Theconfigurations, dimensions, materials, and functions of elements of theliquid core laser ablation catheter 92 may be substantially similar tosimilar elements of the liquid core laser ablation catheter 24 which hasbeen discussed herein. The liquid core laser ablation catheter 92 isshown in order to illustrate the improved cutting ability of the liquidcore laser ablation catheter embodiments 24 having a distal opticalwindow 44 which incorporates an expanded segment 48 as shown in FIGS. 19and 20.

FIG. 18 depicts the liquid core laser ablation catheter 92 disposedwithin a patient lumen 96 ablating target tissue material 90 withoptical energy 89. The optical energy 89 exits an output surface 98 ofthe constant diameter optical window 94 within a first cone angle 100.For contact cutting systems, a hole the size of the optical energy beam89 is created at the output surface 98 of liquid core laser ablationcatheter 92. As shown, this hole may be smaller in transverse dimensionthan the liquid core laser ablation catheter 92. FIG. 19 similarlydepicts the liquid core laser ablation catheter 24 disposed within apatient lumen 96 ablating target tissue material 90 with optical energy89. The optical energy 89 exits an output surface 80 of the expandedoptical window 44 within a second cone angle 102. As can be seen inFIGS. 18 and 19, the expanded segment 48 of the optical window 44 allowsthe optical energy 89 to diverge prior to exiting the output surface 80.Thus the second cone angle 102 of optical energy 89 produced by liquidcore laser ablation catheter 24 provides a greater cutting area than thefirst cone angle 100 of optical energy 89 produced by liquid core laserablation catheter 92. This allows the liquid core laser ablationcatheter 24 to ablate a hole large enough for the distal section 50 ofthe liquid core laser ablation catheter 24 to readily follow into thenewly created lumen.

FIGS. 7 and 8 depict an embodiment of a liquid core laser ablationcatheter 104 which features a non-tapered window housing 106. That is,an outer diameter 108 of the window housing 106 may be constant alongthe length of the window housing 106. The liquid core laser ablationcatheter 104 may incorporate a distal optical window 110 which has anexpanded segment 112 having an outer diameter 114 that is equal to orgreater than the outer diameter 108 of the window housing 106. As withthe distal optical window embodiment 44 of FIG. 2, the distal edge ofthe expanded segment 112 may have a rounded or chamfered corner 113 inorder to facilitate smooth passage of the distal end of the catheterthrough a patient's vessels. Other than the configuration of the windowhousing 106, the configurations, dimensions, materials, and functions ofelements of the liquid core laser ablation catheter 104 may besubstantially similar to or the same as similar elements of the liquidcore laser ablation catheter 24 discussed herein.

FIGS. 9 and 10 depict another embodiment of a liquid core laser ablationcatheter 116 that incorporates an eccentric guidewire lumen 118 which isdisposed on the periphery or outer surface of the catheter body tube 52and extends axially along the outer surface of the catheter body tube52. The guidewire lumen 118 is configured to couple to a suitableguidewire, such as a coronary angioplasty type guidewire, therebyallowing for the ablation of eccentric target tissue materials 90utilizing the liquid core laser ablation catheter 116. Other than theconfiguration of the eccentric guidewire lumen 118, the configurations,dimensions, materials, and functions of elements of the liquid corelaser ablation catheter 116 may be substantially similar to or the sameas similar elements of the liquid core laser ablation catheter 24 whichhas been previously discussed.

Pulsed ultraviolet excimer laser ablation catheter embodiments whichhave been discussed herein may be configured to remove various types ofatheroma by photochemical, photo-thermal and photo-acoustic processes.With this ablative method the irradiated tissue may be removed withlittle to no thermal damage to the edges of the lumen wall of thepatient, because the nanosecond pulse duration of the ultraviolet pulsedexcimer laser currently used for this application is at time scales muchless than the thermal diffusion time of the absorbed optical energy. Thepulsed optical energy from the laser must be delivered inside the bodylumen with a flexible fiber optic or waveguide that can pass thetortuosity of the arterial anatomy of a patient's body to get to thesite of the blockage. A single fiber optic might present an efficientcutting surface, but because the catheter size is in the range of 1 mmto 2.5 mm diameter for the ablation surface, these single fibers at thisdiameter are too stiff for percutaneous use in a patient's body lumen.

Some previous embodiments of ablation catheters use many small diameterfiber optics, typically with cores having diameters of about 50 micronsin quantities of about 100 fiber optics to about 300 fiber optics,arranged in a bundle to provide a flexible ablation catheter in a 1 mmto 2.5 mm diameter. Unfortunately, this cutting surface configurationmay produce a “Swiss cheese” type dead space geometry due to thecladding, packing factor of the multiple fibers, and the outer tube wallthickness. It has been demonstrated that this configuration does not cutas efficiently as a surface with less dead space (such as an ablationcatheter which is configured with a single fiber optic) and requiresmore energy and a higher pulse rate to ablate target tissue.

As has been discussed, an improvement to multiple fiber laser ablationcatheters is the liquid core laser ablation catheter 92 with a soliddistal optical window 94 which is disposed at a distal section 60 of theliquid core laser ablation catheter 92. However, there may still be someresidual dead space due to the cladding material 66 on the distaloptical window 94 and the catheter body tube 52 that contains theoptical fluid 55 and the distal optical window 94. Although thisablation catheter 92 configuration requires lower pulsed optical energyto ablate through target material, the ablation hole which is createdmay be slightly smaller than the outside surface of the ablationcatheter 92 in some cases. This may result in resistance to passage ofthe ablation catheter 92 through target material such as a lesion,especially for a non-compliant lesion such as calcified lesions.

Laser ablation catheters which incorporate the window housing 50 whichincludes the tapered section 51 may have improved maneuvering throughtortuous lesion sites when compared to ablation catheters which do nothave tapered window housings. This is due to the fact that laserablation catheters which incorporate the window housing 50 whichincludes the tapered section 51 have a reduced profile at the catheterdistal section 60 which can more easily pass through tortuous lesionsites within the vasculature of a patient.

The addition of the distal optical window 44 which incorporates theexpanded segment 48 as has been discussed may further improve theability of a given laser ablation catheter (such as liquid core laserablation catheter 24) to ablate through target material 90. Opticalenergy 89 which enters the distal optical window 44 may be transmittedthrough the insert segment 46 of the optical window 44 (where it may beoptically contained by a cladding material 66) and into the expandedsegment 48, that does not include a cladding layer to serve as awaveguide, where it may diverge and exit the expanded segment 48 throughthe output surface 80 of the distal optical window 44. The surface areaof the output surface 80 of the distal optical window 44 may in somecases be greater than or equal to the area of elements which aredisposed at the distal section 60 of the respective laser ablationcatheter such as the window housing 50 or the catheter body tube 52.

Some ablation catheters which utilize the distal optical window 44having an insert segment 46 and an expanded segment 48 may have no deadspace at the output surface 80 of the distal optical window 44. As anexample consider an ablation experiment conducted utilizing two ablationcatheters which incorporate the same size 5 French (1.57 mm) catheterbody tube 52 and a 1.22 mm tapered tip diameter at the distal end. Afirst ablation catheter incorporated a 1 mm diameter distal opticalwindow (constant diameter distal optical window similar to embodiment 92in FIG. 18) and a second ablation catheter incorporated an distaloptical window (enlarged head distal optical window similar toembodiment 24 in FIG. 19) having an expanded section 48 with a diameterof 1.22 mm. Ablation experiments were performed using eachconfiguration, with the enlarged segment 48 configuration of laserablation catheter 24 producing a larger ablation hole than the constantdiameter configuration exemplified in laser ablation catheter 92 and theenlarged segment 48 configuration of laser ablation catheter 24 beingeasier to ablate through phantom targets.

The area of the output surface of a given distal optical window isproportional to the diameter of the distal optical window squared. Thusfor the given example the distal optical window 44 configured with theexpanded segment 48 (1.22 mm diameter) produces a 49 percent largerablation area (output surface 80) for the same diameter optic window 94(1 mm diameter core) with a constant diameter on the same size catheter(5 French). In some cases, the pulse energy from the laser may need tobe increased in order to achieve the appropriate energy fluence over thelarger output surface 80 of the expanded segment 48 of the distaloptical window 44.

As has been discussed, the expanded segment 48 of the distal opticalwindow 44 may be configured with an output surface 80 which has asurface area which is equal to or greater than a surface area of a crosssection of the ablation catheter 24. For some embodiments for treatingperipheral arterial disease where tortuosity is less severe, the distaloptical window 44 may incorporate an insert segment 46 (typically 5 to 8mm length for some embodiments) which may be formed from a single lengthof feed fiber optic. The insert segment 46 may be disposed within thewindow housing 50 and/or the catheter body tube 52 of the liquid corelaser ablation catheter 52. For some embodiments, a proximal portion 59of the insert segment 46 may extend proximally from the interior of thewindow housing 50 and into the inner lumen 53 of the catheter body tube52 as shown in FIG. 4. The distal optical window 44 may also includeexpanded segment embodiments 48 having enlarged diameter 70 that isequal to or larger than the distal portion 68 diameter 72 of theablation catheter 24.

In some cases the distal optical window 44 may be formed from a suitablyconfigured feed fiber optic. The expanded segment 48 may be formed bymelting the cladding material 66 of the feed fiber optic into the innercore of the feed fiber optic within a distal segment of the feed fiberoptic, and then shaping the glass within the distal segment into theexpanded segment 48 after shaping the entire distal optical window 44may be annealed to reduce or remove any stress in the material of thedistal optical window 44. After being formed, the distal optical window44 may be secured (using any suitable adhesive for example) into asuitably configured window housing 50 (as shown in FIG. 17). Theassembly of the distal optical window 44 and window housing 50 may thenbe secured to a suitably configured catheter body tube 52. In somecases, the assembly of the distal optical window 44 and window housing50 may be crimped to the catheter body tube 52 onto the insert segment26 of the distal optical window 44. As has been discussed, the opticalfluid 55 may be disposed within the inner lumen 53 of the catheter bodytube 52. An input optical window 45 may be inserted into the inner lumen53 of the proximal end of the catheter body tube 52 in sealed relationto the inside surface of the inner lumen of the catheter body tube 52.For some embodiments, the input optical window may be made from anultraviolet grade material such as silica, sapphire or the like that areconfigured to efficiently transmit ultraviolet optical energy. A laserconnector 26 may then be attached to the proximal section 28 of theliquid core laser ablation catheter 24.

Some embodiments of the window housing 50 may include at least one crimpridge 67 which may be disposed circumferentially about and extend intothe tube cavity 62 of the window housing 50. Each crimp ridge 67 mayassist in securing the window housing 50 to the catheter body tube 52after the crimping process. Each crimp ridge 67 may be configured as anannular protrusion which extends from an inner surface of the crimpedportion of the tube cavity 62 of the window housing 50 (see FIG. 4) andinto the nominal tube cavity 62. The crimp ridge 67 which is depicted inFIG. 4 is configured with a radiused profile, however embodiments ofcrimp ridges 67 may be configured with any suitable profile such as arectangular profile or a triangular profile.

For some embodiments, multiple crimp ridges 67 may be disposed such thatthey are axially spaced along the interior surface of the tube cavity 62as shown in FIGS. 15-17. Some embodiments of the window housing 50 maybe configured with about 1 to about 5 crimp ridges. For window housingembodiments 50 which incorporate multiple crimp ridges 67, the crimpridges 67 may have an axial spacing of about 0.38 mm to about 0.64 mm.The crimping process which has been previously discussed may result inthe penetration of each crimp ridge 67 of a respective window housing 50into the wall material of the distal section 60 of the catheter bodytube 52 as shown in FIG. 4. The penetration of each crimp ridge 67 intothe wall material of the distal section 60 of the catheter body tube 52may result in a mechanical bond between the window housing 50, thedistal optical window 44, and the catheter body tube 52. In this mannerthe penetration of each crimp ridge 67 into the distal section 60 of thecatheter body tube 52 may act to prevent relative translational motionbetween the window housing 50, the distal optical window 44, and thecatheter body tube 52. Any embodiment of window housings which arediscussed herein may be configured with at least one crimp ridge 67.

Thus, the laser coupler 26 may be optically coupled to the optical fluid55 which is disposed within the inner lumen 53 of the catheter body tube52. The optical fluid 55 is in turn optically coupled to the inputsurface 78 of the distal optical window 44. The input surface may inturn be optically coupled to the output surface 80 of the distal opticalwindow 44 by the insert segment 46 and the expanded segment 48 of thedistal optical window 44. As has been discussed, cladding material 66may be disposed on the outside surface 54 of the insert segment 46 withthe cladding material forming a waveguide configuration facilitating thetransmission of optical energy 89 through the insert segment 46.

In some cases, the catheter body tube 52 may be a fluoropolymer tube.The distal end 60 of the fluoropolymer tube 52 may be notched to areduced outer diameter to attach the window housing 50 such that aproximal portion 64 of the window housing 50 matches the outsidediameter of the catheter body tube 52 after the window housing 50 hasbeen crimped to the catheter body tube 52. In some cases, the windowhousing 50 which secures the distal optical window 44 may also act as aradiopaque marker to locate the distal portion 38 of the liquid corelaser ablation catheter 24 during a procedure which utilizes x-rayfluoroscopy.

The typical NA of waveguide functioning portions of distal opticalwindow embodiments 44 formed from ultraviolet transmitting silica oversilica fiber optics may be about 0.22, thus providing a full cone angleof optical energy 89 of about 25 degrees. The NA of the feed fiberwithin the insert segment 46 of the distal optical window 44 maytransmit through the expanded segment 48 of the distal optical window44. In some cases, the cladding material 66 may be removed from theexpanded segment 48 of the distal optical window 44 during the formationof the distal optical window 44. In some cases the optical energy 89which is transmitted through the insert segment 46 (which may beconfigured as an optical feed fiber) of the distal optical window 44expands in a full cone angle into the expanded segment 48 as determinedby the numerical aperture of the feed fiber which for some embodimentsmay include a full cone angle of optical energy 89 of about 25 degreesas shown in FIG. 12.

The distribution 91 of the optical energy 89 at the output surface 80 ofthe distal optical window 44 may be somewhat Gaussian (again see FIG.12) with most of the optical energy 89 located in the central region andwith lower optical energy at the edges. The degree of centralconcentration is correlated to the overall length 74 of the expandedsegment 48, because the light may radially expand within the material ofthe expanded segment 48 by a full cone angle of about 25 degrees in somecases when it enters the expanded segment 48 which may have no claddingmaterial 66. In some cases the axial length 74 of expanded segment 48may be minimized in order to maintain catheter tip flexibility, andbecause there may be no cladding material 66 to contain the opticalenergy 89 in the expanded segment 48 of the distal optical window 44. Ifthere are too many internal reflections of the optical energy 89 withinthe expanded segment 48, due to, for example, an unnecessarily longaxial length of the expanded segment 48, optical energy 89 may escapefrom an outer surface 83 of the expanded segment 48. The overall length74 of this expanded segment 48 may thus generally be a compromisebetween these factors.

For some embodiments the catheter body tube 52 may be attached to thewindow housing 50 by crimping the proximal portion 64 of the windowhousing 50 onto a distal portion 60 of the catheter body tube 52 and arespective proximal portion 59 of the distal optical window 44. In thismanner the distal portion 60 of the catheter body tube 52 is crimped tothe proximal portion 59 of the distal optical window 44 by the proximalportion 64 of the window housing 50 which may produce a liquid tightseal between the catheter body tube 52 and the distal optical window 44such that the inner lumen 53 is sealed at the distal end of the catheterbody tube 52 by the distal optical window 44. A tube outer surface 61 ofthe catheter body tube 52 may be configured to couple to a housing innersurface 69 of the window housing 50. In some cases, the outer surface 61at the distal portion 60 may be stepped to a reduced outer diameter suchthat after crimping the window housing 50 over the distal portion, thetransition of the outer surface between the catheter body tube 52 andthe window housing 50 is smooth. For some embodiments, the distalportion 60 of the catheter body tube 52 may be bonded into the proximalportion 64 of the window housing 50 with a suitable adhesive 58 such asmedical grade class VI epoxy for fiber optics, with the adhesive 58being disposed between the outer surface 61 of the catheter body tube 52and housing inner surface 69. In some cases, an inner lumen of theproximal portion 64 of the window housing 50 may be expanded to aninside diameter which is greater than an outside diameter of the distalportion 60 of the catheter body tube 52 in order to facilitate assemblyof the device and couple to the distal portion 60 of the catheter bodytube 52. In turn, as discussed above, the distal portion 60 of thecatheter body tube 52 may optionally be notched or suitably tapered inorder to couple to the proximal portion 64 of the window housing 50thereto.

In some cases, it may be desirable to have the distal optical window 44configured as a modified fiber optic because a distal optical windowwhich is configured as a bare ultraviolet silica rod would failoptically as a waveguide. This is because either the adhesive 58 or thewindow housing 50 inner surfaces (56, 69) of the window housing 50 wouldabsorb the optical energy 89 configured as ultraviolet light, or anyother suitable wavelength range of optical energy, which is transmittedthrough the distal optical window 44 for such an embodiment, as it wouldnot be refracted from the interface between the distal optical window 44and the adhesive 58. This is because such an adhesive 58 is not likelyto be configured to transmit or refract the optical energy 89. In orderto properly function as a waveguide, such a bare window substrate wouldneed to be coated with a low index of refraction coating, a dielectric,reflective metallic coating or the like. In some cases the axial length74 of the expanded segment 48 of the distal optical window 44 may beonly about 1 mm, and the exit angle of the optical energy 89 emittedfrom the insert segment 46 may have a full cone angle of about 25degrees into the expanded segment 48 (as shown in FIG. 12). Thus, mostof the optical energy 89 for an embodiment with a bare insert segment 46would escape through outer side surfaces the insert segment 46 of thedistal optical window 44 which is configured with no cladding material66, and would be absorbed by the window housing 50.

In some cases it may be desirable to improve the distribution 91 of theoptical energy 89 (see FIG. 12) within the expanded segment 48 of thedistal optical window 44 by using distal optical window embodiments 44with insert segment embodiments 46 having a silica over silica fiberoptic structure with a large numerical aperture. Distal optical windowembodiments 44 including a large numerical aperture silica over silicafiber optic structure may produce greater divergence for optical energy89 being emitted from the core of the insert segment 46 into thematerial of the expanded segment 48 of the distal optical window 44. Asan example, a fiber optic structure with a silica over silicacore-cladding arrangement for the insert segment 46 with an NA of 0.30yields a cone angle of about 35 degrees for optical energy emitted fromthe insert segment 46 into the expanded segment 48 that will haveimproved expansion within the expanded segment 48 of the distal opticalwindow 44. In addition, a better match of the respective indices ofrefraction of the optical fluid 55 and material of the distal opticalwindow 44 may also be useful to reduce coupling losses at the interfaceof two materials with differing indices of refraction. The convex outputsurface 84 of the expanded segment 48 of the distal optical windowembodiment of FIG. 13 may act to concentrate the optical energy 89emitted from the expanded segment 48 to produce a higher energy fluencein the middle of the beam relative to the energy fluence of the opticalbeam 89 in the insert segment 46 portion of the distal optical windowembodiment 44. The concave output surface 88 of the distal opticalwindow embodiment which is depicted in FIG. 14 may act to expand theoptical energy 89 emitted from the center of the expanded segment 48 tothe edges of the expanded segment 48, in order to smooth out theGaussian-like energy distribution 91 such as may be generated from aflat output surface 80 as shown in FIG. 12.

For some liquid core laser ablation catheter embodiments, the process ofcrimping the window housing 50 onto the catheter body tube 52 and thedistal optical window 44 offers improved adhesion strength over someprevious embodiments particularly since adhesives do not typically bondwell onto fluoropolymers such as Teflon® or FEP. The distal opticalwindow 44 may be bonded to the window housing 50 as has been previouslydiscussed, and the proximal section 64 of the window housing 50 may beconfigured to couple to a distal section 60 of the catheter body tube52. The proximal section 64 of the window housing 50 may then be crimpedonto the distal section 60 of the catheter body tube 52 and theinsertion segment 46 of the distal optical window 44 by any suitablemeans. For example, the crimping process may be accomplished by asuitably configured crimping machine.

The compression of the window housing 50 onto the catheter body tube 52and the insert segment 46 of the distal optical window 44 may act toform a hermetic seal between the window housing 50 and the catheter bodytube 52 in some cases. The crimped configuration, particularly with theuse of internal ridges 67 that penetrate an outer wall of the distalsection 60 of the catheter body tube 52, may also improve adhesionstrength of the junction between the window housing 50, the distaloptical window 44 and the catheter body tube 52. The strength of thisjunction may in some instances be indicated by destructive pull forcetesting which may be performed on multiple such assemblies. In somecases the ridges 67 upon being embedded in the wall material of thedistal section 60 of the catheter body tube 52 may mechanically capturethe distal section 60 to the window housing 50 which may be particularlyuseful for embodiments using fluoropolymers (such as FEP) for thecatheter body tube 52 which may have a very low coefficient of frictionand be generally slippery and ill suited for adhesive bonding. Improvedadhesion strength may be achieved with the use of a distal opticalwindow embodiment 44 which is formed from a fiber optic. The distaloptical window 44 formed from a fiber optic may be configured with alength which is long enough to achieve a good hermetic seal, but withthe overall length 74 of the distal optical window 44 being axiallyshort enough to keep the distal section 60 of the ablation catheter 24flexible so as to maintain the capability of going through curves in apatient's anatomy such as vascular lumens and the like.

The entirety of each patent, patent application, publication anddocument referenced herein hereby is incorporated by reference. Citationof the above patents, patent applications, publications and documents isnot an admission that any of the foregoing is pertinent prior art, nordoes it constitute any admission as to the contents or date of thesepublications or documents.

Modifications may be made to the foregoing without departing from thebasic aspects of the embodiments discussed. Although embodiments havebeen described in substantial detail with reference to one or morespecific embodiments, those of ordinary skill in the art will recognizethat changes may be made to the embodiments specifically disclosed inthis application, yet these modifications and improvements are withinthe scope and spirit of the disclosure.

Embodiments illustratively described herein suitably may be practiced inthe absence of any element(s) not specifically disclosed herein. Thus,for example, in each instance herein any of the terms “comprising,”“consisting essentially of,” and “consisting of” may be replaced witheither of the other two terms. The terms and expressions which have beenemployed are used as terms of description and not of limitation and useof such terms and expressions do not exclude any equivalents of thefeatures shown and described or portions thereof, and variousmodifications are possible. The term “a” or “an” can refer to one of ora plurality of the elements it modifies (e.g., “a reagent” can mean oneor more reagents) unless it is contextually clear either one of theelements or more than one of the elements is described. Thus, it shouldbe understood that although embodiments have been specifically disclosedby representative embodiments and optional features, modification andvariation of the concepts herein disclosed may be resorted to by thoseskilled in the art, and such modifications and variations are consideredwithin the scope of this disclosure.

Certain embodiments of the technology are set forth in the claim(s) thatfollow(s).

What is claimed is:
 1. A laser ablation catheter to ablate blockages inbody lumens, comprising: a liquid filled waveguide including an elongatecatheter body tube having an inner layer with a first index ofrefraction and an optical fluid disposed within an inner lumen of theelongate catheter body tube, with the optical fluid having a secondindex of refraction which is greater than the first index of refraction;and a distal optical window disposed in liquid sealed relation to asurface of the elongate catheter body tube at a distal end of theelongate catheter body tube, the distal optical window including: aninsert segment which is disposed within the inner lumen of a distalsection of the elongate catheter body tube, and an expanded segmentwhich is disposed distally of the insert segment, which comprises amaterial configured to efficiently transmit optical energy for ablationof blockages in body lumens, which has an outer diameter which isgreater than an outer diameter of the insert segment, and which has anaxial length sufficient to allow optical energy expansion within theexpanded segment.
 2. The laser ablation catheter of claim 1 wherein theinsert segment comprises silica or sapphire.
 3. The laser ablationcatheter of claim 1 further comprising a layer of material disposedabout an outer surface of the insert segment which includes an index ofrefraction lower than an index of refraction of the material of theinsert segment or a reflective material.
 4. The laser ablation catheterof claim 1 wherein the inner layer of the catheter body tube comprisesan amorphous fluoropolymer.
 5. The laser ablation catheter of claim 3wherein the layer of material disposed about the outer surface of theinsert segment comprises an amorphous fluoropolymer.
 6. The laserablation catheter of claim 3 wherein the layer of material disposedabout the outer surface of the insert segment comprises a reflectivematerial and further comprises a dielectric material or metal.
 7. Thelaser ablation catheter of claim 1 wherein the expanded segment is notconfigured to act as a waveguide.
 8. The laser ablation catheter ofclaim 1 further comprising an input optical window disposed in liquidsealed relation with a proximal end of the catheter body tube.